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Abstract: The spectroscopic properties of tellurite glasses of composition (in mol%) TNKNd: (70− x)TeO2–15Nb2O5–15K2O–xNd2O3 (x =0.1, 1.0, 1.5, 2.0 and 2.5) and TNLNd10: 69TeO2–15Nb2O5–15Li2O–1.0Nd2O3 and lithium metaborate glass of composition LBNNd10: 89LiBO2–10Nb2O5–1.0Nd2O3 have been investigated using absorption and emission spectra and decay curve analysis. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands, using the free-ion Hamiltonian model. The spectral intensities have been calculated by using the Judd–Ofelt theory and in turn the radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The decay curves at the lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (⩾1.0mol%) due to energy transfer processes. The effective lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration for all the glasses under investigation. The non-exponential decay curves have been well-fitted to the Yokota–Tanimoto model with S =6, indicating that the nature of energy transfer is of dipole–dipole type and energy migration also plays an important role. The results obtained have been compared with Nd3+-doped phosphate, fluorophosphate, lead borate, tellurite, germanate and silicate glasses and Nd3+-doped YAG ceramic and Ca2Nb2O7 crystals. [Copyright &y& Elsevier]

Abstract: This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm3+ and Dy3+ doped chloroborate glass matrices of the compositions 69.5B2O3 xLiCl(30− x)NaCl0.5R2O3 and 69.5B2O3 xLiCl(30− x)KCl0.5R2O3 (where R=Sm and Dy and x =5, 10, 15, 20 and 25). Using Judd–Ofelt theory, the spectral intensities and Judd–Ofelt intensity parameters (Ω 2, Ω 4 and Ω 6) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and peak emission cross-sections (σ P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm3+ ion, the transition, 4G5/2 → 6H9/2 shows highest emission cross-section and is maximum at x =10mol% in lithium–sodium and at x =20mol% in lithium–potassium glass matrices. For Dy3+ ion, the transition, 4F9/2 → 6H13/2 shows highest emission cross-section and is maximum at x =20mol% in lithium–sodium and at x =10mol% in lithium–potassium glass matrix. [Copyright &y& Elsevier]

Abstract: Spectroscopic characterization for optical amplification and laser application of the Er3+-doped Bi4Si3O12 glass is performed through its absorption and luminescence spectra. The spontaneous radiative transition probabilities from the first seven excited states to the ending states are calculated to obtain the luminescence branching ratios and radiative lifetimes. Intense infrared to visible luminescence of the Er3+ ion is observed with 4I9/2 state excitation (800nm) under a 200mW laser excitation power. The value obtained for the ratio of the 4I11/2 → 4F7/2 excited-state absorption oscillator strength to the 4I15/2 → 4I11/2 ground state absorption oscillator strength is in accordance with those reported for Er3+-doped materials pumped efficiently at 4I11/2 level excitation wavelengths. Gain cross-section spectra as a function of the inverted population rate and the stimulated emission cross-section spectrum were determined for the 4I13/2 → 4I15/2 infrared (IR) laser transition. The large gain bandwidth of the 4I13/2 → 4I15/2 IR emission has resulted in being close to those reported for Er3+-doped oxide glasses suitable for broadband amplifiers. [Copyright &y& Elsevier]

Abstract: 53.3BiO1.5–33.3GeO2–13.4NaO0.5 (cation%) glasses with various Tm3+ concentration were prepared by melt-quenching method. These glasses show high density, high refractive index, low phonon energy and good stability against crystallization. Absorption spectra of Tm3+-doped bismuthate glass were measured to obtain the radiative lifetimes by Judd-Ofelt theory. The absorption (4.5×10−21 cm2) and emission (6.7×10−21 cm2) cross-sections were calculated by Beer–Lambert and McCumber theory. The results show that the Tm3+ (3F4 → 3H6) in these glasses have high spontaneous radiative transition probabilities and large stimulated emission cross-section. Then the fluorescence emission spectra were measured under 808nm excitation and the maximum emission intensity at 1.8μm is obtained at 0.9mol% Tm2O3 in the glasses. [Copyright &y& Elsevier]